feat: pass slack thread context to llm as message_history

[brijsiyag-meesho]

Description

Previously, Slack integration was using single_message_history but wasn't passing this to LLM for previous context.
This solution just passes all thread messages as message_history so LLM can get context of the thread.
Also we are not storing anything at onyx side so it shouldn't be issue in terms of slack

How Has This Been Tested?

Manually

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---

Summary by cubic

Added per-message history with token counting for Slack threads to improve context management and prevent token overflow in long conversations.

• New Features
  • Introduced message_history parameter in stream_chat_message_objects.
  • Slack handler builds a list of PreviousMessage with token_count using the persona’s tokenizer.
  • Passes message_history and single_message_history to chat processing, with a safe fallback when message_history is None.

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[greptile-apps]

Greptile Overview

Summary

This PR adds a message history parameter with token counting functionality for Slack integration. The main changes include:

• Enhanced stream_chat_message_objects() - Added optional message_history parameter that allows passing pre-calculated PreviousMessage objects with accurate token counts
• Improved Slack token counting - Updated Slack handler to calculate token counts for each message in the thread history using the LLM's tokenizer before creating PreviousMessage objects
• Better performance - By pre-calculating token counts in the Slack handler, this avoids duplicate tokenization work and provides more accurate token counting for Slack thread contexts

The implementation maintains backward compatibility through proper null checking and fallback logic. When message_history is not provided, the system falls back to the existing behavior of creating message history from history_msgs.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• This is a straightforward enhancement that adds optional token counting functionality. The changes maintain backward compatibility through proper null checking, use appropriate type annotations, and follow the existing codebase patterns. No breaking changes or risky modifications.
• No files require special attention

Important Files Changed

File Analysis

Filename	Score	Overview
backend/onyx/chat/process_message.py	5/5	Added optional message_history parameter with proper type annotation and fallback logic
backend/onyx/onyxbot/slack/handlers/handle_regular_answer.py	5/5	Added proper token counting for message history and pass calculated message_history to stream_chat_message_objects

Sequence Diagram

sequenceDiagram
    participant SlackHandler as Slack Handler
    participant TokenCount as Token Counter
    participant ProcessMsg as Process Message
    participant PreviousMsg as PreviousMessage

    SlackHandler->>+TokenCount: check_number_of_tokens(message, tokenizer)
    TokenCount-->>-SlackHandler: token_count
    
    SlackHandler->>+PreviousMsg: PreviousMessage(message, role, token_count, files=[], tool_call=None, ...)
    PreviousMsg-->>-SlackHandler: message_history_item
    
    SlackHandler->>+ProcessMsg: stream_chat_message_objects(message_history=message_history)
    
    ProcessMsg->>ProcessMsg: Check if message_history is None
    alt message_history is provided
        ProcessMsg->>ProcessMsg: Use provided message_history with token counts
    else message_history is None
        ProcessMsg->>ProcessMsg: Create message_history from history_msgs using PreviousMessage.from_chat_message()
    end
    
    ProcessMsg-->>-SlackHandler: answer_stream

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[brijsiyag-meesho]

@Weves currently this PR contains some patchy solutions, if team thinks we can proceed with this than I will polish the code further.

[cubic-dev-ai]

1 issue found across 2 files

Prompt for AI agents (all 1 issues)

Understand the root cause of the following 1 issues and fix them.


<file name="backend/onyx/chat/process_message.py">

<violation number="1" location="backend/onyx/chat/process_message.py:256">
Comment above this line is now misleading (describes a string). Update/move it to document single_message_history and add a brief comment for message_history.</violation>
</file>

_{React with 👍 or 👎 to teach cubic. Mention @cubic-dev-ai to give feedback, ask questions, or re-run the review.}

[cubic-dev-ai]

Comment above this line is now misleading (describes a string). Update/move it to document single_message_history and add a brief comment for message_history.

Prompt for AI agents

Address the following comment on backend/onyx/chat/process_message.py at line 256:

<comment>Comment above this line is now misleading (describes a string). Update/move it to document single_message_history and add a brief comment for message_history.</comment>

<file context>
@@ -253,6 +253,7 @@ def stream_chat_message_objects(
     # a string which represents the history of a conversation. Used in cases like
     # Slack threads where the conversation cannot be represented by a chain of User/Assistant
     # messages.
+    message_history: List[PreviousMessage] | None = None,
     # NOTE: is not stored in the database at all.
     single_message_history: str | None = None,
</file context>